2 What is a PVR Backend and why do I need it?

A PVR Backend is the actual software that interfaces with your tuner hardware and handles the recording. XBMC simply acts as a graphical interface to this software, allowing you to access it from within XBMC.

5 Do I need to separately download PVR add-ons or do they come bundled with XBMC?

Official XBMC.org versions of XBMC for Android, iOS, Mac OS X, and Windows, come with PVR add-ons already included with XBMC. Linux users will need to install PVR add-ons using the instructions for their specific PVR backend. See PVR backend.